The long-term goal of this project is to determine the nature of the associations established when infrahuman organisms (rats, pigeons, and goldfish) are exposed to various explicit or implicit dependencies between discrete external stimuli, drive states, contextual cues, and responses. The phenomena of sign-tracking (which include autoshaping and the feature positive effect) serve as major tools for investigating learning, memory, and performance. Current work on the psychological significance of the "absence" of some stimulus will be continued in studies of trace conditioning and discrimination learning based on a single distinguishing feature; and our enduring interest in inhibitory processes reveals itself in planned work on the extinction, spontaneous recovery, and disinhibition of conditioned inhibition. Various relations between CSs and USs (spatial proximity, modality differences, temporal contiguity, backward pairings, partial reinforcement, type of information about US provided by CS) will continue to be explored in auto-shaping and conditioned-suppression tasks. The proposed work seems significant with respect to the applicability of response-centered vs. perception-centered approaches to learning, the validity of the Rescorla-Wagner conditioning model, the role of reinforcement in learning performance, and the utility of "surprise" and "informativeness" as explanatory concepts.